The former Massachusetts governor and head of Bain Capital will join Solamere Capital, where his son Taggart serves as a managing partner, a person with knowledge of the matter said. Mr. Romney is expected to spend a portion of his time serving as chairman of the firm’s executive committee, the person added.

A letter has gone out to investors announcing the news, said the person.

Solamere Capital, founded in 2008, is led by Taggart Romney, along with Eric Scheuermann, a former partner of Jupiter Partners, and Spencer Zwick, who was once deputy chief of staff during Mr. Romney’s tenure as Massachusetts governor.